<?php
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$xhtml = array(
	'<{title}>' => 'Part of the site blocks me while another part doesn&apos;t',
	'takedown' => '2017-11-01',
	'<{body}>' => <<<END
<img src="/img/CC_BY-SA_4.0/y.st./weblog/2019/03/01.jpg" alt="A path through the snow" class="framed-centred-image" width="649" height="480"/>
<section id="drudgery">
	<h2>Drudgery</h2>
	<p>
		My discussion post for the day:
	</p>
	<blockquote>
		<p>
			When we build a decision tree, we&apos;re trying to reduce the level of entropy each time we branch.
			We&apos;ve got to decide what branching criteria is best suited for this.
			To do that, we measure the information gain for each prospective branching criterion <a href="https://www.math.unipd.it/~aiolli/corsi/0708/IR/Lez12.pdf">(Aiolli, n.d.)</a>, choosing the one that would get us the most information should we add it to the tree at the given spot.
			When using classification trees, or decision trees used to classify things, we&apos;re trying to predict a qualitative property instead of a quantitative one.
			We can&apos;t use mathematics to find the information gain based on the values used in classification groups though; those values aren&apos;t numeric in classification trees.
			Instead, we find the classification error rate, which is based on how many test cases in the group are in the most common classification opposed to those that are not.
			Alternatives to the classification error rate exist though, in the form of Gini indexes and cross-entropy <a href="https://www-bcf.usc.edu/~gareth/ISL/ISLR%20First%20Printing.pdf">(James, Witten, Hastie, &amp; Tibshirani, 2013)</a>.
			I can&apos;t get into how those are calculated though due to the length limit of this assignment.
		</p>
		<h3>Examples</h3>
		<p>
			One example of where a decision tree is used in all our lives is in telling where to store your food.
			Let&apos;s say you&apos;ve moved into a new apartment.
			Your cupboards, refrigerator, and freezer are bare, and you&apos;ve just brought in your first groceries.
			For each item, you need to ask questions.
			Is the item perishable?
			If yes, it should probably be kept cold.
			Is it something that would be damaged by being frozen?
			If yes, it goes into the refrigerator.
			If no, is it something you either need to cook or will be stored for a long period of time?
			If yes, it goes in the freezer.
			If no, it also goes into the refrigerator.
			If the item isn&apos;t perishable, further questions are needed there as well, such as how often you plan to access that type of food and how heavy it is.
			You probably don&apos;t want to store your heavy cans in the upper cupboards, and instead want them near the floor, for example.
		</p>
		<p>
			A creepier example is websites that try to up-sell to you.
			They take a look at your past purchases and/or what&apos;s in your shopping cart at the moment, and use it to find the things you&apos;re most likely to buy.
			They can&apos;t throw the whole catalogue at you on the checkout page, but they can recommend a few items they think you would be interested in.
		</p>
		<div class="APA_references">
			<h3>References:</h3>
			<p>
				Aiolli, F. (n.d.). <a href="https://www.math.unipd.it/~aiolli/corsi/0708/IR/Lez12.pdf">Microsoft PowerPoint - TextCategorization.ppt - Lez12.pdf</a>. Retrieved from <code>https://www.math.unipd.it/~aiolli/corsi/0708/IR/Lez12.pdf</code>
			</p>
			<p>
				James, G., Witten, D., Hastie, T., &amp; Tibshirani, R. (2013). <a href="https://www-bcf.usc.edu/~gareth/ISL/ISLR%20First%20Printing.pdf">An Introduction to Statistical Learning with Applications in R</a>. Retrieved from <code>https://www-bcf.usc.edu/~gareth/ISL/ISLR%20First%20Printing.pdf</code>
			</p>
		</div>
	</blockquote>
</section>
<section id="card">
	<h2>Credit card</h2>
	<p>
		The snow&apos;s cleared up enough that the postal service can finally deliver the mail.
		Even the bike path is clear enough to use now!
		As such, the new credit card arrived.
		Several places, in big writing, instructions tell you to download a garbage mobile application and use it to activate the card.
		No, thank you.
		In small print, instructions say to activate on the Web if you don&apos;t have a mobile device.
		Yeah, that&apos;s what I thought.
		They&apos;re not going to deny service to people that don&apos;t want t install the application, they just want to make that look like the only way to people that aren&apos;t paying attention, and if they are opposed enough to doing that, they&apos;ll look over the instructions more carefully and find the Web-activation instructions.
	</p>
	<p>
		It seems though that while the page to register for a card doesn&apos;t block me, the page to activate one does.
		The pages used to contact customer support block me too.
		There&apos;s nothing I can do as far as this card is concerned.
		It&apos;s a useless chunk of plastic.
	</p>
</section>
END
);
